LARP (Laser Activated Remote Phosphor) technology is known from the prior art. Here a conversion element is irradiated with an excitation beam (pump beam, pump laser beam) by an electromagnetic radiation source. The conversion element here includes or consists of a phosphor. The radiation source is a laser light source or a light emitting diode (LED). Excitation radiation incident in the conversion element is at least partly absorbed and at least partly converted into conversion radiation (emission radiation). The wavelength and thus the spectral properties and/or a color of the conversion radiation are/is determined in particular by the phosphor. The conversion radiation is emitted in all spatial directions. If full conversion is not present, (at least in part, depending on the layer thickness and concentration of scattering centers of the conversion element) the non-converted excitation radiation is also emitted or scattered in all spatial directions. The emission radiation emitted from an element side is usually used further by an optical unit (optical component).
If the phosphor of the conversion element is applied to a (diffusely) reflective support, then LARP technology can be used in a reflective embodiment. As a result, both a converted excitation radiation and a scattered excitation radiation that penetrates through the phosphor are then reflected back from the reflective support into the phosphor and “recycled”. In contrast to this reflective embodiment, in the case of a transmissive arrangement of the phosphor, use is often made of a dichroic mirror provided in the beam path between the radiation source and the conversion element (advantageously as near as possible to the conversion element). The excitation radiation can penetrate through said dichroic mirror, which has a reflective effect for the conversion radiation, that is to say for radiation in converted wavelength ranges. As a result, a “recycling” effect can be achieved in the transmissive embodiment, too.
What is disadvantageous about the cited LARP technology is the comparatively low luminous efficiency.